A problem with the polymerization of vinyl monomers is the development of a progressive deposit on the internal surfaces of a polymerization reactor, more specifically on the internal wall of the reactor and the surfaces of the impeller, baffles and so on.
A deposit on the internal surfaces of a polymerization reactor not only detracts from the reactor cooling efficiency but, upon detachment of the deposit and entry of the deposit into the product polymer, adversely affects the quality of the product polymer. Furthermore, much labor and time are required for removal of the deposit after the polymerization reaction. Therefore, more than a few methods comprising application of build-up suppressants have heretofore been proposed.
For example, Japanese Examined Patent Publication (Kokoku) No. 30343/1970 teaches the use of polar organic compounds such as thioethers. Japanese Examined Patent Publication No. 363/1990 discloses condensates of phenolic compounds with formaldehyde or benzaldehyde. Japanese Unexamined Patent Publication (Kokai) No. 34241/1989 (EP0027466) discloses a reaction product of a thiodiphenol and a bleaching agent. U.S. Pat. No. 4,555,555 describes condensates of pyrogallol or hydroxyhydroquinone with aromatic aldehydes. U.S. Pat. No. 4,431,783 teaches a 1-naphthol-formaldehyde condensate. Japanese Unexamined Patent Publication No. 132907/1987 teaches polysulfide rubbers.
However, some of these proposed suppressants tend to reduce the polymerization rate or detract from the quality of the product polymers, while others are not sufficient in the suppressant effect or only effective for a limited time. Thus, all of them remain to be improved.